Tutorials - Lines of Position, Ranges, and Fixing Positions

Lines of Position and Ranges

Guild of Cartographers lesson

This brief and highly visual tutorial is to assist apprentices in the Guild of Cartographers with creating highly accurate maps. Using lines of position is a far better way of identifying locations than "pacing it out."

When you positively know the location of an object, it is said to be "fixed." The process of identifying this location is known as "fixing," and the process of identifying your own location is "taking a fix."

What is a line of position (LOP)? Quite simply, it's an imaginary line between any two points. In cartography and navigation, this usually translates to a bearing, from your position to an object on the map/chart. Frequently, this is expressed as degrees clockwise (0-359) from True North.

Here is an image of an IRL nautical chart, to which I've simulated my position on the water; I ran three LOPs, one from a water tower, and two from buoys. The intersection of the three red lines is my simulated location. (Warning: never take an actual LOP from a buoy, as they may move if they drag anchor or as the tide changes)

Finding an LOP in the game interface is sort of an art form. You must have both objects lined up in the center of the screen. I run the program windowed at 800x600 and have a centered background image on my desktop, which helps me center the window on a lubberline. Here's my background for accomplishing good LOPs. It's a 1024x768 bitmap which I center on my desktop. The black box in the middle is where the game interface should sit, and the red line extending out the top and bottom of the black box is my lubberline, or the direct center of my 800x600 game window.

Here's an image showing an LOP from the "origin," or point I started my map, to the furthest point of a crack in the floor, which I'm trying to "fix."

If you are able to get LOPs from two known points to your position, you have an assumed position. If you can get LOPs from three or more known points, you have fixed your position. On the map/chart, you simply draw these LOPs, and where they intersect is where you are. Occasionally, your LOPs will create a polygon instead of an exact point. This is referred to as a "bad cut," because the LOPs should "cut" the point in half. The accepted practice here (in real-life navigation) is to derive the position as the center of the polygon. In most instances, it will be close enough.

Here's two other LOPs to the point I wish to fix.

Occasionally you can find two objects that line up vertically when you are looking about. The LOP through these two objects, assuming that the objects are fixed and their positions known, creates what is known as a range. If you can view the two objects in their lined up position, you are "on the range." If you cannot, you are not "on the range," even though the range exists.

Here are a few images that illustrate ranges. The first uses lights on either side of the fountain along with the center of the fountain. The second uses two manually positioned cones.

Sometimes, you are afforded the ability to make your own ranges. If you're in an area with cones or other moveable objects, you can use them along with known points to create a range and thus fix the position of unknown objects. In the following image, I've done exactly that - I've placed a cone at a known location and lined it up with both another known location and an unknown location.

Sure, now you want to know how I know the position of the cone? That's easy. Many areas have floor patterns which repeat and thus make a good scale for drawing new maps. When you first arrive in an area, try to locate a large, repetitive floor pattern which will help you draw much of your new map. In the following image, I've highlighted a single tile, which is the basic unit of measure I'm using in this area. Simply count the tiles from either "edge" of the map to fix the location of the cone.

Once I've nailed the LOP, I can transfer it to my map. Do it a few more times, and I'll know the exact position of the beginning of the crack.

--Apprentice Dohati Endetan